We are attempting to define the genetic basis of cell-cell recognition. As a first step, we plan to characterize the genes encoding the major histocompatibility complex--the transplantation antigens--by the use of recombinant DNA technology. Our initial efforts have been directed towards obtaining cloned cDNAs corresponding to these genes. To find these cDNAs clones techniques have been developed which allow the rapid screening of hundreds of cDNA clones. We are currently characterizing clones containing beta-2 microglobulin cDNA and are trying to find clones containing H2 cDNA sequences.